That looks like a good healthy chicken poop! Despite the build up around her vent, it doesn't appear to be blocking her poop. Some clear liquid with the poop is not necessarily unusual.
That looks like a nice sized set up for Rosey. I have learned through experience that the chicken poop can soak through news paper pretty fast. If you haven't layered something under the newspaper, your big box will get damp on the bottom. You might also want to prevent spillage from the waterer. One of the best things that I have used is a cut down half gallon or gallon plastic jug. Leave the handle on it and cut out the rest to form a bowl. Then anchor the jug handle to the side of the enclosure. I would cut a couple of little holes and feed a long twistie-tie through. The other option is to put some sort of plate under the waterer, but I didn't find that this worked as well. I guess I have been frustrated too many times by waterers got knocked over and soaked everything.
Nice work with the roost.